Pulse shaping is desirable in many applications involving ultrafast laser pulses. A notable example of such an application is the adjustment of pulse bandwidth to enhance pulse compression and consequently enable the generation of pulses having a shorter duration than those obtained directly from an ultrafast laser oscillator. Pulse shaping can be achieved through the well-known technique of spatially dispersing the spectral content of a pulse using a diffraction grating, transforming the pulse into a Fourier-plane using appropriate imaging optics, then manipulating the amplitude or phase of the dispersed spectral-components of the pulse in the Fourier-plane using a spatial light modulator (SLM). The modulated spectral components are then re-transformed to the time domain with an additional imaging optics and a second grating or by back-propagating the pulse through the input optics in reverse order to obtain a modified (temporally shaped) pulse.
Most prior-art such pulse-shaping schemes are commonly optimized for a specific pulse bandwidth and can yield degraded performance when attempting to manipulate pulses with spectral content differing from that anticipated by the nominal optical configuration. Schemes for shaping pulses having different spectral bandwidths are described in U.S. patent application Ser. No. 11/602,147, filed Nov. 20, 2006, assigned to the assignee of the present invention and incorporated herein by reference. All of these schemes are complicated by a preference for locating the SLM in a Fourier-transform plane (Fourier-plane). Apparatus for implementing the schemes is relatively complex and relatively bulky, for example having a volume of about 1 cubic foot. It would be useful if acceptable pulse-shaping performance could be achieved by simpler and more compact apparatus. It would also be useful if a compact pulse-shaping apparatus could also provide pulse compression thereby eliminating the need for additional apparatus for providing this function